1. Field of the Invention
The present invention relates to an electrophoresis apparatus in which nucleic acid, protein, or the like is separated and analyzed by electrophoresis, particularly to a capillary electrophoresis apparatus.
2. Description of the Related Art
Usually a laser light source is used as an excitation light source in the capillary electrophoresis apparatus. However, recently use of a light emitting diode (LED) for the excitation light source is propose to reduce cost of the capillary electrophoresis apparatus. USP 2003/0178312-A1 discloses an electrophoresis apparatus in which LED is used.
Japanese Patent Application Laid-Open No. 5-52810 and Japanese Patent No. 2833119 disclose an electrophoresis apparatus in which the laser beam is not emitted in a direction perpendicular to a capillary axis, but excitation light is emitted in a capillary axis direction. The excitation light propagates through the capillary to excite a detection target substance migrating in the capillary without imposing any restriction on a position of the detection target substance. A wide excited region, i.e., a wide detected region is acquired, which allows sensitivity to be enhanced in the electrophoresis apparatus. The detection light from a linear light emission portion is dispersed with a diffraction grating and detected with a two-dimensional detector.
U.S. Pat. Nos. 6,821,402 and 6,863,791 disclose a conventional method of acquiring spectral data.
Earnest study of inventor reveals the following problems. In the electrophoresis apparatus disclosed in Japanese Patent Application Laid-Open No. 5-52810 and Japanese Patent No. 2833119, because the capillary in itself is used as both an excitation unit and a detection unit, there is generated the problem that a detection position is shifted by capillary exchange. Therefore, it is necessary to acquire spectral data in each capillary exchange. When the spectral data is incorrect, a pull-up signal is generated in an analysis process due to the wavelength shift. With increasing wavelength shift, the pull-up signal is increased to reduce reliability of analysis result.
In the spectral data acquiring method disclosed in U.S. Pat. Nos. 6,821,402 and 6,863,791, the actual electrophoresis is required for a known sample, which takes a large amount of time for an operator.
That is, in the method in which the diffraction grating is used, the spectral data acquisition is required in each capillary exchange while the simultaneity can be ensured between the sensitivity and the data acquisition. On the other hand, in the method in which the plural filters are used, the simultaneity cannot be ensured between the sensitivity and the data acquisition while the spectral data acquisition is eliminated in each capillary exchange.
In view of the foregoing, an object of the invention is to provide a capillary electrophoresis apparatus in which the simultaneity can be ensured between the sensitivity and the data acquisition to decrease the pull-up signal while the spectral data acquisition is eliminated in each capillary exchange.